I just purchased a c 6 that had a np 208 behind it. It came with the aluminum adapter. I am trying to put the 205 behind it, but it does not have the notch for the shift rails, so it won't mate together unless I notch it. Is it ok to notch this adapter myself, or will it be weak after doing this. I was also wondering if this works, and I build a good cross member can I put a doubler behind the aluminum adapter.

Notch away, but make shure you use some sort of t-case support like the factory did- or better.

In post #74 in my buildup thread there is a pic of what a factory C6-NP205 adapter should look like. It will be fine to notch yours. The t-case cross member and frame support bracket (which is used with the NP205) should take most of the load from the T-case, the tranny/adapter should only support the front of the 205.

Oddly enough, I am using a NP208 adapter and it has an Atlas hanging off of it. No issues at all.